1. Field of the Invention
This invention relates to a vapor generating and recovering apparatus for vaporizing a liquid and maintaining the vaporized liquid in a vapor state in a container having an open top, and more particularly, to such an apparatus using a hot surface for substantially vaporizing immediately all of a condensed vapor.
2. Description of the Prior Art
Vapor generating and recovery apparatuses are well known for use in surface treating various objects. The surface treating can be a cleaning treatment wherein foreign material, such as, for example, oil or wax is removed from the surface of the object, or a recovery treatment wherein a contaminated chemical is purified by distillation, or a heat emitting treatment for shrink fitting, or a heat absorbing treatment for reflowing metals. Regardless of the exact nature of the surface treatment, the objects to be surface treated are, typically, immersed into a vapor of an appropriate surface treating material. As the liquid boils, the vapor is recovered for reuse in the treating process.
In some instances, objects to be surface treated are at a sufficiently low temperature relative to the temperature of the vaporized liquid. When these relatively cold objects are immersed in the vapor, the objects initially and rapidly absorb enough heat from the treatment vapor to condense this vapor to a liquid. When this happens, the vapor zone collapses. The time required for revaporizing the liquid is lost to the treatment process thereby extending the time required to complete the treatment operation. This lost time increases costs, particularly when the treatment process is a step in a high volume manufacturing operation.
One example of a heretofore known apparatus is taught in U.S. Pat. No. 3,947,240 issued on Mar. 30, 1976. The apparatus is for generating a vapor for soldering, fusing or brazing articles. The apparatus includes an open topped vessel having a heating coil in the portion end and cooling coils between the top and bottom of the vessel. An eutectic solder heated by the heating coil forms a molten pool over the bottom of the vessel. A liquid to be vaporized forms a pool floating or forming a stratified layer of liquid on top of the molten pool of eutectic solder. The liquid is brought to and maintained at a boil by the heat of the molten solder which acts as a heat transfer medium between the heating coil and the liquid.